You're completely right, this definitely uses GNU extensions. A note about the __VA_ARGS__ detail - You can portably avoid it in a lot of cases if you plan ahe

You're completely right, this definitely uses GNU extensions. A note about the __VA_ARGS__ detail - You can portably avoid it in a lot of cases if you plan ahead and allow __VA_ARGS__ to suck-up one extra always-provided argument, but it's not as clean as the GNU extension and can't always be done.